I found out who this is for. It is for the guys who are sensitive to the ESS sound. It sounds more like a clean CS43198 than a clean ESS dac - which it should. I like both equally for what they bring to the table.
Last comment was for the Questyle…
Shozy by receiver. CS43131 being old isn’t enough reason to dismiss this based on implementation, but also at that point it’s a larger ES100 for $150-$200 with updated Bluetooth and 4.4mm instead of 2.5mm
The dongle market is 500% saturated, I always hope that the occasional BT receiver releases at least have something new to offer especially at that asking price.
Why get this over a BTR7 (with a helpful display for volume level), Musehifi M4, Q5K, BTR13, etc?
Especially as it’s unlikely that they have a fully fledged app with PEQ, although I don’t know.
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Yeah but I haven’t heard anyone accuse the M15(OG) of having an “ESS sound”, that’s the thing. So you have both of them and have been able to A/B? I was under the impression the C was some freshly announced product, showing not in stock because it’s never been in stock yet.
I have both right in front of me. Amazon US has them. So, in my ears I hear some very minor brightness, or ESS glare / sheen on the 15i. Everyone hears a little different. It is very minor but I can’t not hear it. I have always been sensitive to this. In addition I believe the CS is slightly warmer and has slightly fuller vocals. In addition I like these better than the Moonriver Ti, DC04 Pro, and the Aful Snowy Night.
I also can’t listen to most metal dome speakers but that is another issue.
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Are you sure the Mt6xx series has LED underlighting…? I have Xduoo MT602 and Xduoo TA-20+ - the MT602 doesn’t sound tube like at all but that is down to the config - they are using a negative feedback loop just like the Cayin uses and I imagine the Muse would also due to the layout, offerings and dimensions. Hybrid tube amps are a bit gimmicky. I would need to get it out and try it out as it been awhile now but IIRC the tube glows after power off and takes time to warm up to a full glow. Here is a picture of the board - not sure I see the LED on a quick glance
I think regarding the LEDs we are getting in chicken and egg territory… In general I choose to be very careful with brain perception explanations as it is an open invitation to the “my truth” subjectivism at all costs that renders everything meaningless and provides allowances for manufacturer untruths ie we just chuck a fake tube or no tube at all in any dongle but as long as it has LED underlighting it will sound warm and musical… Those studies that talk about glow effects do not account for previous associations or hearsay experiences which aid the brain in creating it’s anticipatory experiences.
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I am not sure in a way I disassembled one, but I read at least couple of people on reddit who said there is a LED backlight for those tubes (with audiophile-heaven as one, not my favourite source of audio information btw). EDIT - but your experience proves otherwise. Unless it is well designed to act in such a fucked up lying way - with large cap still powering up the LED after the power off, so it looks naturally 
Are those some kind of caps or LEDs indeed?
In regards to the justification of adding LEDs - I also don’t like this kind of approach unless it is explicitely explained in the marketing material that backlight is for aesthetic purpose only (as indeed it looks nice).
On the other hand I believe tubes may be placed in there working completely fine, but just not glowing visibly due to the implicit design choice of not putting so much current through them or them being more efficient. And just because we humans don’t see in IR then it may seem to the users like those are not fully functioning.
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I would actually have respect for the effort in the deception
My understanding is that you should optimally place the LED on the underside of the socket instead of the centre to get a more realistic diffused glow - also easier to connect. It appears orange - saw another image where one looks to have depth to it - I’m really unsure - I’ll get it out this week and have a look.
Are there non/low glow tubes that function efficiently on low current & voltage…? If that is the case then I see where your going with the led plus these in a portable - but without good efficiency you are probably flooding the SQ with distortion and little else as the tube would be more like a preamp…
I have prejudice from 25 years of using temperamental guitar tube amps where if they don’t glow something either isn’t working properly or about to not be working properly. I only have a couple of OTL headphone tube amps (along with the hybrids & portables) so not that knowledgeable or experienced on this topic.
P.S. Sorry everyone - will stop this tube chat so normal service of releases can be resumed on this thread
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Gotcha gotcha. Thanks for the info! I’ve also looked at the price difference in the meantime and yeah… this could also be for people who want to hear Questyle’s current-mode amplification magic for a way lower price than before. 
For my needs though… I don’t think I’m ready to give up on the glare/sheen part of it, so I can’t see myself getting this version, even though I’ve seen other 43198 dongles being called “bright” before, so it might be the closest thing to an ESS that’s not an ESS, in the current market. Also I’m afraid of the power draw now that I’ve seen what the KA17 can do to my phone. 
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Not that it matters but I wasn’t calling the 15i bad in any way… just not better for me. I listened to these most of the day and almost keep both for different reasons but ended up just keeping the M15c. Side note - I cant wait to get the KA17 again when they release the mating battery.
Yeah, saw that as well.
Maybe it should’ve come with it from the start, but then people might’ve been scared away by even more chonk. But it could’ve been better than what I saw with my old 10000 mAh Xiaomi power bank and my Oppo HA-2 used as a power bank, i.e. that neither of those can power the KA17 beyond what my Lenovo P2 phone can offer, so with or without them the KA17 on such an old phone isn’t even able to surpass the Hiby FC3’s high-gain power, which is around 112 mW @ 32 ohms (but paradoxically it does drain the phone considerably more, and this is with PEQ off).
Really bad surprise for me how picky the KA17 is with the setup it needs to really show its best performance, and even then you lose brightness vs. other ESS products. That should teach me to ever trust FiiO’s marketing again, and even reviewers hyping a product, even if most of them are in agreement.
I believe most of these tube amps do work like that and is why they are technically Hybrid Tube amps.
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Oops, the power plot thiccens.
Did you find by any chance the 15C was able to push 2x the power on BAL-out vs. the 15i?
I currently only use 3.5 to keep the output impedance as low as possible. Don’t know if it matters but it makes me feel better… On both of my iems I am only adjusting the volume to 25% or less so I don’t need the extra power at all.
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If its under 1ohm, then it wont really matter. Unless u have something like the Andromeda which is extremely sensitive to OI changes.
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